At present, some telecom operators have many networks with different modes, for example, China Unicom has the GSM (Global System for Mobile Communications) network and the WCDMA (Wideband Code Division Multiple Access) network, China Mobile has the GSM network, the TD-SCDMA (Time Division Synchronous Code Division Multiple Access) network and the TD-LTE (time division long-term evolution) network. Currently, the voice service in the LTE network uses the CSFB (Circuit Switched FallBack) technology for voice call and requires the LTE terminal in the LTE network to fall back to the GSM network or any other voice-enabled network, which requires the LTE terminal to support the LTE mode and other modes, and support quickly switching between the LTE mode and the other modes.
Moreover, the LTE terminal needs to achieve the co-transmission of PS (packet switched) data and CS (Circuit Switched) data in the LTE network, and the LTE terminal needs to simultaneously support working simultaneously in the LTE mode and other modes. In the current mobile terminal users, one user will have more than one USIM (Universal Subscriber Identity Module) card/SIM (Subscriber Identity Module) card, and different cards are in different networks or each USIM card/SIM card corresponds to a different network, which requires the mobile terminal to support single-card multi-mode and multi-card multi-standby.
FIG. 1 is an architectural block diagram of the radio frequency section of a conventional dual-mode dual-standby terminal, comprising two independent power management chips (PMUs), two independent radio frequency chips, two independent digital baseband chips, two independent SIM card sockets and two independent clock sources. Because it comprises two independent digital baseband chips and two independent power management chips, a larger area is occupied during the layout. There are two independent SIM card sockets, two SIM cards with different modes cannot be arbitrarily placed within any one card socket, while the USIM/SIM card in any card socket can be read or written in any mode, thus achieving the multi-mode multi-standby, but not the switching to the multi-mode single-standby mode.